As I am sure others will tell you, there are many unseen benefits to Driver Training days and it's not until you have taken part that you realise certain things such like:-
The full potential of a
standard Impreza.
The gains of modified brakes.
The advantages of modified suspension.
Tyre choice.
Also a safe way (& often the first time) of experiencing issues such as:-
The feel of weight transfer due to high speed cornering.
Your cars reaction to braking hard at high speeds.
The limits of your brakes (which often isn't as good as you would imagine)!
Finding optimum rpm for up/down shifting.
Finally, as Gary (Morley WRX) mentioned you learn a lot about yourself. If most guys were honest you soon find out that you are know where near as good as you thought you were, which suggests that these courses work.
I have done bits & pieces of low key motor sport including National Karts, A Lister Jag in the Supercar Challenge run by the Lamborghini Owners Club, Navigating in Clubman level rally events and a few other bits, and I still find Training days good fun as I am still learning.
Still learning the P1 at moment too

.
562 Bhp/1290 Kg's is a bit of a friggen handful to be honest (Jolly Green & such guys will know what I am talking about).
Under hard acceleration & hard braking the car feels soooooo light ! and steer correction requires rapid reflexes.
The VERY WET Brands track day that many SES guys attended was my first
time out with 562 in the wet.
From Surtees & into Clearways at the pit entry point I was on the floor in 3rd, into 4th over the brow & I had traction issues in both gears. Steer correction was about every 10th of a sec to keep it looking straight and although brilliant fun I also realised that the chances of smashing the car to bits was really high, which was not an option, so I called it a day at 2.30.
With Project 2 hopefully finished end of 2010 I am now wondering if 650 Bhp in a car that weighs nothing is a sensible idea?